6x6 1/10 Off Road Truck build

[MadInventor 3884]

Need some chains holding those logs on. Was a bit of 'Final Destination' moment there in the video. Look out for anyone following!

My thoughts exactly, Half of the times I had to cut the video was due to the load coming loose.

[bromvw 744]

Unfortunately there's no extra room at the front for a reduction unit, and tbh, I like the fact that it has a good turn of speed in 3rd gear. It will go slowly in 1st, it's just I did not drive it like that in the video. Also, if I added a reduction gear, all I would have would be 3 slow speeds. I like the fact that I cannot just pull off in 3rd (Like with the Hi-Lifts for instance), but that you have to use the lower gears to build up speed first. There is the possibility of moving the gearbox rearwards about an inch, which would make room for a 4274 2000KV brushless motor in the front, this was going to be my final option if the silver can didn't have the power, but I think it's quite well balanced as is, and I don't want to rebuild this for a 3rd time I'm still suffering with radio signal issues, but I think this is down to the aluminium cab acting like a farady cage. Most of the antenna is loosely coiled in the bottom of the cab, with only the contents of the antenna outside (and this can be shielded by the cab when it's facing towards me). I'm going to pull the antenna through and see if it improves the situation with more of it outside the cab.

I'm really quite pleased with this, considering that it's a 5kg truck, towing a 1kg trailer, with at a least a 1kg of wood on it, and the fact that the diffs aren't locked, it got stuck remarkably little. I also plan to make a tow pin that has a body clip retaining it, so that the trailer doesn't part company with the truck again when I go over bumps at speed Dot take me wrong Martin lol . its always better to have some speed in reserve . it does look like a heck of a lot of fun . Hope you can sort out the signal issues .

[MadInventor 3884]

I've made some more progress on the truck, despite having 'finished' it a while ago......

I got a new headache bar made. The frame is steel tube TIG welded together by a friend, with the inner bars being solid aluminium rod. This weighs about half what the old one did (which was all steel) and I think this one looks better too.

I also got the cross members welded to the chassis, making it a lot stronger, and also had a number plate panel welded to the back as well. It got resprayed with a slightly different paint scheme, and I stripped the paint off the bolsters as they were starting to look untidy.

I've also secured the tow bar with a push pin as well as screws, to prevent it from twisting in the chassis.

[IBIFTKH 1369]

Every time I look at this build it blows my little mind. It's an amazing concept and the reality is just awesome. It's a proper beast and very cool. Major congrats on an a fantastic build, I hope it brings you much enjoyment.

[djmcnz 754]

Do you even need the alu tube in the bars? May add marginal but still unnecessary weight?

[MadInventor 3884]

Do you even need the alu tube in the bars? May add marginal but still unnecessary weight?

The rods are scale in quantity and spacing for the trailer I copied the idea from, so I wanted to try and keep it like that. Also, individually, the rods are not that strong, so if I thinned them out I would probably end up with them being being bent after being used for a while.

[djmcnz 754]

Ah, okay makes sense.

[MadInventor 3884]

Been quite a while since I've done any work on this model, I've just been putting 'miles' on it driving it round the garden for my son. Whilst still trying to decide on the way forward on my grapple skidder, I decided to try and give it a bit of a power upgrade. The motor it's been using for the last 2 years is a Mabuchi silver can running a 9.6V NimH battery, but it's starting to feel a bit tired, I wanted to put some more oomph behind it, and sort out a few more issues while I had it to pieces. I decided to try and fit an EzRun 4274 2000KV brushless system in it.

The reasoning being that

a.) I'd already got one in my TXT-1, so had one to hand to try,

b.) it's physically bigger by quite a margin than a silver can, and should produce a lot more torque

c.) I can run it on 4S if I want to, and it will easily cope with the 3S LiPo I've already got.

The first problem was the shift servo being mounted in front of the silver can and there not being enough room to fit the 4274 motor in. To get around this, I cut a hole in the side of the chassis and made a custom brass shifter linkage to slide in the slot in the chassis, so that I can operate the shifter from a servo in the cab.

This works really well, as it gets rid of the problem with the normal linkage method of the shifter rotating when it's pushed by the servo. This shifter is captivated by the chassis, and makes it far easier to set up and get a consistent performance from.

The next problem to overcome was the fact that the screws holding the gearbox together were in the way of the motor, thanks to it's larger diameter. To get around this I made a spacer plate 4mm thick, and the same diameter as a 540 (36mm).

Next I had to fit the servo to operate the linkage. Firstly I drilled a hole in the front of the cab to allow the shifter rod to pass through it, then made some risers to mount the servo on.

The servo was then fitted vertically inside the cab:

I'm also decided to try and get the fan working fitted to the front of the rad casing, as it is now directly in front of the motor, so I machined out the rad casing to allow maximum throughput of air for the fan.

I'm nearly ready to try it now, I've fitted the brushless motor with a 15 tooth pinion as I didn't have anything smaller. I'll hopefully be able to jerry rig an ESC and battery into it in the next couple of days and see what it goes like. It will be interesting to see if the gearbox destroys itself on the first run, as I'm running a heavy model with a 1/8 brushless motor, when Mr T recommends nothing pokier than a silver can and a 7.2V battery.

Other mods I've got planned are moving the front axle forward a bit to accommodate TLT-1 wheels and tires on the front axle, and possibly some form of sprung suspension to replace the tractor suspension. If as I suspect the truck is going to be quite quick, some shock absorption on the front axle would be a good idea given the amount of weight sitting on it. I might also have one last attempt at getting lights onto it and working.

[IBIFTKH 1369]

It didn't look slow with the silver can. Brushless with 3S or 4S is going to be insane! I hope you have some heavy duty shin pads...

[MadInventor 3884]

I've just got back in from trying the truck.

I've been lied to, there is such a thing as too much power.

Basically, I didn't check the operation of the gear shifter and pulled off in 3rd instead of 1st. Truck did a wheelie and threw one of the front tires, and that was going uphill !!. I ran it around on the road for a few minutes and then found that the Loctite holding one of the diff gears onto the drive shaft had broken under the torque onslaught. I only noticed once I found that what I thought was 3rd was actually 1st and tried it in 1st and found the front wheels spinning. I'm just trying to decide now whether to repair it and then try running it again to get a video, but I think it definitely too much power and won't be trying it on 4S. Funnily enough, the gearbox seems fine....... I think I'm going to have to try and find something a little less savage, but will try it again when I can get it into 1st and 2nd before 3rd.

[neverfollow 599]

You really have earned your username. Great job!

[emory70 153]

Too much power? Perish the thought.

I've seen some of your work, and it's quite impressive. One thing I can't figure out is how do you figure out how to align gears in a transmission? Is there a formula for using pitch and # of teeth to determine where to drill for the axle? Or is it much more complicated?

[MadInventor 3884]

Too much power? Perish the thought.

I've seen some of your work, and it's quite impressive. One thing I can't figure out is how do you figure out how to align gears in a transmission? Is there a formula for using pitch and # of teeth to determine where to drill for the axle? Or is it much more complicated?

It's not difficult to do. basically, take the module of the gear, then multiply it by the number of teeth, and this gives you the PCD (Pitch centre diameter) of the gear. This is basically the diameter that runs through the centre of the gear tooth. For example a mod 1.0 gear with 25teeth would have a 25mm PCD. This would mean that in theory 2 25tooth gears would need to be 25mm apart for a perfect mesh. I then add 0.1mm to that dimension to give a small amount of room for play and manufacturing error. This seems to work quite well, without the gears binding.

As another example, a mod 1.0 50 tooth gear meshing into a 14 tooth gear would give 50/2 + 14/2 = 25+ 7 = 32mm (+0.1) distance between centres.

Gears with the same tooth count, but with 0.8module would give 50*0.8/ 2 + 14*0.8/2 = (50 + 14)*0.4 = 26.5mm (+0.1) distance between centres. You can also do the maths for mod 0.1 to start with, then multiply the result by 0.8.

This gives the distance between the centres. The layout of the gears is then down to trig (Lots of sin, cos, tan, and triangles, if it's not a straightforward straight line layout) . Makes me smile when I think back to trig lessons at school and we were all thinking, 'What are we ever going to use this for in real life ?????'

[neverfollow 599]

It's not difficult to do. basically, take the module of the gear, then multiply it by the number of teeth, and this gives you the PCD (Pitch centre diameter) of the gear. This is basically the diameter that runs through the centre of the gear tooth. For example a mod 1.0 gear with 25teeth would have a 25mm PCD. This would mean that in theory 2 25tooth gears would need to be 25mm apart for a perfect mesh. I then add 0.1mm to that dimension to give a small amount of room for play and manufacturing error. This seems to work quite well, without the gears binding.

As another example, a mod 1.0 50 tooth gear meshing into a 14 tooth gear would give 50/2 + 14/2 = 25+ 7 = 32mm (+0.1) distance between centres.

Gears with the same tooth count, but with 0.8module would give 50*0.8/ 2 + 14*0.8/2 = (50 + 14)*0.4 = 26.5mm (+0.1) distance between centres. You can also do the maths for mod 0.1 to start with, then multiply the result by 0.8.

This gives the distance between the centres. The layout of the gears is then down to trig (Lots of sin, cos, tan, and triangles, if it's not a straightforward straight line layout) . Makes me smile when I think back to trig lessons at school and we were all thinking, 'What are we ever going to use this for in real life ?????'

My head just exploded lol

[MadInventor 3884]

I've been hard at work on the truck today. I decided to leave the motor in for 1 last run, so have rebuilt it ready to go again. Whilst looking at the possibility of fitted a 4 link system to the front axle, I noticed that the axle rotation felt a bit notchy. So I took it to bits and found this:

The front pinion drive for the axle was somewhat destroyed, with a tooth missing and the lots of metal floating around inside the diff housing. Fortunately I had a spare TLT-1 item, so that went in to replace it. I've also put a hole the rear of the cab near the ESC and run the main power leads out through the bottom of the cab. I found some Velcro straps to hold the 3S on with, and made up a short in series connector to run the rad fan directly off the battery. This means that the motor should get some cooling all the time, and if it does get hot, I can turn the truck off and still leave the motor cooling fan running. I also made an antenna post so that I could mount the antenna on the top of the cab, rather than poking it in one side of the headache bar frame.

Velcro straps and bettery installation:

Motor and cooling fan installation:

I had to chop the side of the bonnet slightly in order to feed the cable through for the motor.

The finished article rebuilt and ready to go:

I'm hoping to go and carefully run it on a large expanse of tarmac tomorrow afternoon, and will try and get some video at that time. I'll also try it on 2S if I don't break it on 3S, to see if it is a little more manageable. Seems a bit of a waste though, to run a 4S motor on 2S. I think the motor and speedo are likely to find their way back into my TXT-1, and I'll have to look for a cheap low KV motor to go into this.

[emory70 153]

Ok, I have no idea what mod is in relation to what we call it here in the states. We just use pitch (32, 48, 64). So pitch is teeth per inch. How does mod relate to pitch, as we call it?

[MadInventor 3884]

Ok, I have no idea what mod is in relation to what we call it here in the states. We just use pitch (32, 48, 64). So pitch is teeth per inch. How does mod relate to pitch, as we call it?

module is the metric equivalent of diametrical pitch (32, 48dp, etc). So for example, a mod 1.0, or module 1.0 gear has a tooth 1mm wide. 0.8 module is 0.8, etc. 32dp is equivalent in size to 0.8module if I remember rightly. Diametrical Pitch (DP) is a measurement of the number of teeth per inch I believe, hence the reason as the number increases so does the number of teeth on a given diameter

[emory70 153]

Groovy. Thanks

[MadInventor 3884]

Took the truck out for a re-try with the brushless motor and 3S today. Definetly too much power. Wheelies slightly changing up from 1st to 2nd.

http://youtu.be/v6CxfhiZE4s

Crashed it:

http://youtu.be/hdt5z9GvkeY

I've now to take it apart and assess the damage, as it was making bad grinding noises when I tried pulling off in 1st. I shall remove the 4274 and put something a little less brutal in it. Maybe go back to the silver can, but run it on 3S, although I would like to put a brushless system in it for the torque, and a little bit more speed than the silver can

Edit 06/10/2014:

The total damage from the crash was:

1 broken ball joint on the rear shock mount

4 damaged gears in the gearbox where the grub screw came out of the motor pinion and rattled through the box.

3 grub screws came loose in one of the walking beams

1 bent bolster on the trailer

1 dented roof panel

1 dented front wheel

Considering the weight of the truck i think I got off lightly, the loose grub screws were just down to too much power working them loose, but it's clear that the motor is far too fast for the model. I've refitted a silver can for the time being, and when I get time I will look at getting a 12V brushed ESC for it so that I can run the 540 on 3S. I've also bought another 3 racing light kit which I am going to fit when I get a chance, and I also want to add a bit more detail to the cab.